Locking apparatus for a telescopic boom



Marqh 18, 1958 J. P. WAITE 2,827,186

LOCKING APPARATUS FOR A TELESCOPIC BOOM Filed Nov. 17, 1955 5 INVENTOR. JoHN R M11" 2,s27,1ss

LOCKING APPARATUS non A rurnscorrc aoolvr John P. Wmte, Miiwauhee, Wis, assignor to H. P. Waite, Inc, Milwaukee, Wis, a corporation at Wisconsin Application November 17, 1955, Serial No. 547,435

4 Claims. (Cl. 214141) This invention relates to power operated construction apparatus, such as a back hoe, crane or the like, and more particularly to a power operated apparatus having a telescopic boom.

When using a back hoe it is often desirable to change the length of the boom in order to meet the requirements for a specific digging operation. It is convenient to have a boom that can be readily lengthened or shortened as desired, particularly when digging around obstructions such as trees, pipe, etc. Similarly, it is often desirable to have a variable length boom for a crane so that the length of the boom can be readily changed to meet the requirements of a given operation.

At present there are power operated telescopic booms which are lengthened or shortened through operation of a hydraulic system. Not only is a hydraulic system expensive due to the pumps, valves and other high pressure equipment that is required, but a hydraulic system 18 not readily adaptable to existing machines. For example, it

is not feasible to drive the pump of a hydraulic system from the drum motor of an existing back hoe or crane due to the complicated speed reduction mechanism which would be required. Therefore, to install a hydraulic system for actuating a telescopic boom on an existing machine requires the addition of a separate power unit to operate the hydraulic system.

The present invention is directed to a simple and inexpensive apparatus for varying the length of a boom. The apparatus not only can be installed on new machincry but can be applied to existing machines without the need of a separate hydraulic system and without altering parts, with the exception of making the boom telescopic, or changing the operation of the machine.

According to the invention, the boom is composed of two telescopic members which are slidable with respect to each other to increase and decrease the length of the boom. A hydraulic cylinder is attached to one of the boom members and the Working end of the piston rod carried bythe cylinder is attached to the other of the boom members. A closed conduit connects the opposite ends of the cylinder and permits hydraulic fluid contained within the cylinder to pass freely from one end of the cylinder to the other as the piston moves within the cylinder in accordance with relative movement of the boom members. The boom members are locked in relation to each other to hold the boom at any desired length by a valve which is disposed in the conduit and is adapted to cut ofi the flow of fluid therethrough.

The boom is extended or retracted either by operation of the drag and hoist lines While holding the dipper in a fixed position or by elevating or lowering the boom and permitting gravity to slide the boom members in relation to one another. When the boom members are at the proper extended or contracted position to give the desired boom length, the valve is closed, thereby locking the boom members in this position and providing the boom with the desired length.

2,827,186 Patented Mar. 18, 1958 ice The present invention is of simple construction and does not require a separate hydraulic system and the accompanying valving and pumping members. In ad--' dition, the present apparatus may be quickly and easily operated, for the operator has merely one valve control to actuate in order to lock the boom at a desired length. There is no complicated control system such as that which usually accompanies a hydraulic system.

The present construction can be readily adapted for use with existing machines without alteration of parts or changing the operation of the machine. As no complicated hydraulic system is required and as high fluid pressures are not involved in the present apparatus, the maintenance problem is at a minimum.

The drawings illustrate the best mode presently contemplated of carrying out the present invention.

in the drawings:

Figure 1 is a diagrammatic side elevation of a back hoe embodying the present invention;

Fig. 2 is an enlarged fragmentary side elevation with parts broken away in section and showing the hydraulic system for locking the boom members in positions with relation to each other;

Fig. 3 is an enlarged sectional view of the hydraulic cylinder employed for locking the boom at a given length; and

Fig. 4 is an enlarged transverse section taken along lines 4-4 of Fig. 2

The drawings illustrate a power operated back hoe or drag shovel having a cab 1 which houses the drive mechanism and is rotatable on crawlers or treads 2.

A telescopic'boom is secured to the cab and is composed on a pair of boom members 3 and 4 which are slidably interconnected to provide the boom with a variable length. The inner end of inner boom member 3 is pivotally connected to a pair of lugs 5 which extend upwardly from the front of cab 1. A dipper stick 6 is pivotally secured to the outer end of the outer boom member 4 and the dipper stick carries a dipper 7 which is adapted to penetrate and dig into the material to be excavated.

The dipper 7 and dipper stick .6 are pivoted about the boom to move the dipper in the digging and dumping strokes by a cable 8 which is secured to cable drum 9. Cable 8 passes over sheaves 10 and 11, which are rotatably secured to the upper surface of inner boom member 3, and sheave 12, which is secured to the forward edge of the dipper. The cable is dead-ended on the boom, as indicated by 13. With this sheaving arrangement the dipper 7 is drawn inwardly toward the machine as the cable 8 is retrieved and moves outwardly away from the machine as the cable 8 is let out.

The boom is raised and lowered by a conventional sheaving system in which a cable 14, secured to cable driun 15, passes over sheaves 16 and 17 and is dead-ended on arms 18. The arms 18 are pivotally attached to the upper end of dipper stick 6 and rotatably support the sheave 17. The sheave 16 is rotatably secured to the outer end of mast 19 which extends upwardly from the cab 1. By retrieving cable 14, sheave 17 is moved toward sheave 16 thereby pivoting the boom upwardly about the forward portion of the cab, while letting out cable 14 serves to pivot the boom downwardly with respect to the cab.

Each of the boom members 3 and 4 are provided with a generally box-shaped cross section with the outer member 4 having a lesser dimension than the inner member 3 so that the outer member is slidable within the inner member.

The length of the boom can be increased .by retrieving drag cable 8 and slacking off on the hoist cable 14 while i the boom.

therein by. any conventional means.

suitable opening in pin 22. As the inner end portion boom member 4 moving inwardly, piston system and thereby lock the members and trieved while again maintaining the dipper in a fixed position and slacking off on the drag cable 8. This action telescopes the outer member 4 into the inner member and thereby shortens the length of the boom.

Gravity can also be employed to shorten or lengthen the boom. Toshorten the boom length,,the boom is pivoted upwardly to a dumping position and'the outer boom member 4 will then slide downwardly within the inner member. Conversely, by lowering'the boom down into an excavation, the force of gravity will cause the outer boom member '4 to slide downwardly away from the inner member 3 and thereby incr'easethe length of Suitable guides and ways may be used withboom members 3 and 4, if desired, to facilitate the sliding, movement of member 4 which respect to member 3.

To lock the outer boon'imember 4 withrespect to boom member .3 and thereby secure the boom at any desired length, a hydraulic cylinder is disposed within the telescoped boom members and is adapted to contain a hydraulic fluid. The inner end of the cylinder 20 is provided with a pan of lugsZl which receive a pin 22. 'The pin 22 is disposed through suitable aligned openings in the side walls of the boom member 3 and is locked A piston 23 is siidably. disposed within the cylinder 2t} and carries a piston rod 24 which extends outwardly through suitable packings in both ends ofihe cylinder. The inner end portion of piston rod 23 is slidably disposed within a of rod 23, extending inwardly beyond the piston, is

' approximately equal tofthe length 'of the outer-portion of the rod extending outwardly beyond the piston, the effective volume of'the cylinder on either side of the piston, when the piston is at the center of the cylinder, is the same.

The outer or working'end of rod 24 is enlarged, as

indicated at 25,-and receives a pin 26. The pin 26 is suitably secured within alignediopenings in the side walls of the outer boom member 4 and serves to connect 4 piston rod 24 to boom member 4.

With this construction, as the boom member dis extended or retracted, the piston 23 is moved corresponding- 1y within the cylinder 29. U

To providea closed hydrauliesystemfor the hydraulic fluid, a conduit 27 is connectedbetween fittings 2B and 29 which are securedwithin openings in the oon site end portions of cylinder 20. The conduit 27. estamgshes communication between the opposite end portions of the cylinder, and as the boom member 4% is moved withmrespect to boom member 3, the piston 23 moves within the cylinder 20 to displace fluid from one end of thecyiinder through conduit 27 to the opposite end of the cylinder. For example, as the b oom member 4 ismoved outwardly with respect to boom member 3 to increase the. length of the boom, the piston23 is moved outwardly within the cylinder thereby forcing fluid from thefouter end of cylinder Zilthrbughcondilit 2.7 to the inner end of the cylinder. When the 'boom'lngth is shortened by 23 moves in wardly within cylindeiZG to force fluid irorhlthe inner end of the cylinder through conduit 27 to the outer end thereof. 1 p

To cut off the new of fluid withinjthe closed hydraulic with respect to each other, a valve Si) is disposed inthe eon' duit 27. yalve 3G may-either be manually or autoat a given length.

plated that the valve 30 can be operated by the operatorof the machine either by a flexible cable, electrically or by any other convenient means.

In operation of the present apparatus, the valve 30 is initiallyopened and the boom member 4 is extended or contracted with respect to boom member 3, in the manner set forth previously, to give the desired boom length. Valve 30 is then closed to lock the boom members against relative movement and hold the boom at the given length. If a change of boom length is subsequently desired, valve 30 is imerely" opened and the boom member 4 is again moved to obtain the desired length. 7

While the present description is directed to the'cylinder 2% being attached to the inner boom member 3 and the piston rod 24 being attached to the outer boom member 4, it is contemplated that the cylinder can be connected to boom member land, the piston rod to boom member 3. Similarly, the cylinder and piston rod structure can be located outwardly of the boom members rather than within the same, as shown in thedrawiugs. f V V m The present'inverition' provides a simple apparatus for varying the length of a telescopic boom and locking the boom at the desired length. The apparatus may readily be adapted for. use with conventional back hoes, cranes or other apparatus having a boom which can be varied in length.- 1

Variousmodes of carrying out the invention are contemplated as within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

Iclaim: V 1. In atpower operated apparatus, a boom having a pair of telescopieboom members with said members being slidable with respect to each other to increase and decrease thelength of the boom, a cylinder to contain hydraulic fluid and attached to one of said members, piston means freely slidablewithin said cylinder and connected to the other of said members, conducting means providing communication between opposite end "portions of the cylinder with the fluid being free to flow from one end portion of the cylinder through said cotnduc tin g means to the opposite end portion of the cylinder as said piston means moves within the cylinder, -and.valve means associated with saidconductiug means to cut off the flow of fluid therethroughand prevent relative movement of the 'boom membersand thereby lock the boom at a given length.

2. in a power operated apparatus, a supporting struc-' end portions of said reservoir, a hydraulic fluid disposed 7 within said reservoir, a ram freely slidable within said reservoir and connected to the other of said boom members, separate means for moving said boom members'with respect to each otherto increase and decrease the length of the boom with said ram moving within said reservoir in accordance with relative movement of said boom members and displacing ,aquantity of iiuid from one end portion of said reservoir through said conduit means to the other end portion'oi' said reservoir, and valve means associated with said conduit meansrand having an open and closed position, the' open positionof said valve means permitting fluid to pass throughsaid conduit means and thereby perfree. relativemovemept of said boom members and the closed .positionof the v ailvei closing off the flow of fl d u a d ,cqa ui m a s tnt reb k i o members withrespect to eachother and hold the boom 3. In a power operated iapparatuspa supporting struci hire, a boom includinga first boom member pivotally enemas connected to the supporting structure and a second boom member supported by said first member and movable in relation to first boom member to increase and decrease the length of a boom, a cylinder to contain hydraulic fluid and pivotally attached to one of said members, piston means freely slidable within said cylinder and pivotally connected to the other of said members, conduit means providing communication between opposite end portions of the cylinder, separate means for moving said boom members with respect to each other to increase and decrease the length of the boom with said piston means moving Within said cylinder in accordance with relative movement of said boom members and displacing a quantity of fluid from one end portion of said cylinder through said conduit means to the other end portion of said cylinder, and a valve member disposed in said conduit means and having two operative positions, the first of said positions permitting fluid to pass through said conduit means and thereby permit free relative movement of said boom members and the second of said positions closing off the flow of fluid through said conduit means to thereby lock the boom members with respect to each other and hold the boom at a given length.

4. In a power operated apparatus, a supporting structure, a boom including an inner member pivotally connected to the supporting structure and an outer member supported by said inner member, both of said members having a generally box-shaped cross section and said outer member being freely slidable with respect to the inner member to increase and decrease the length of the boom, a cylinder adapted to contain a hydraulic fluid disposed within one of said members and connected thereto, piston means freely slidable within said cylinder and connected to the other of said members, fluid conducting means providing communication between opposite end portions of the cylinder with the fluid being free to flow from one end portion of the cylinder through said fluid conducting means to the opposite end portion of the cylinder as said piston means moves within the cylinder, and valve means associated with said conducting means to cut ofi the flow of fluid therethrough and prevent relative movement of the boom members and thereby lock the boom at a given length.

References Cited in the file of this patent UNITED STATES PATENTS 2,196,649 Waite Apr. 9, 1940 

